The present invention provides a reverse flow cyclone separator. The present invention has particular applicability in domestic vacuum cleaners, where dust and other debris are separated from air, although phase separation of other materials including separation of two liquids is envisaged.
In a cyclone separator, a fluid mixture is swirled in a container which swirling motion causes the heavier components of the mixture to move preferentially to the outer region and the lighter components to move to the inner region. By supporting a flange centrally across the container leaving a gap between it and the outer wall, the components can be separated because the heavier components pass through the gap while the lighter components at the smaller radii are constrained by the flange. There is a problem however that the swirling lighter components may pick up heavier components after they have been separated if the flange and gap do not present a sufficient barrier. This leads to inefficiency in the separation process and may also clog filters or other screens located downstream of the container.
The present invention provides a reverse flow cyclone separator comprising a container closed at one end, means for introducing a fluid mixture swirling about an axis at a region of the container remote from said end, barrier means between said region and said end, the barrier means having a surface facing said introducing means and extending towards the outer wall of the container leaving a gap therebetween, and an outlet for lighter phases of the mixture, the outlet opening from said region, the barrier means having an outer perimeter which extends in the axial direction a distance not less than the radial extent of said gap. Since the outlet opens from said region, the flow of fluid from the fluid introducing means to the outlet is not obstructed by the barrier and does not pass through the gap.
The barrier means may have a solid outer perimeter which is continuous in said axial direction; in a less preferred alternative the means may comprise a plurality of separated barriers spanning an axial distance not less than the radial extent of said gap. If the barriers are of different radial extents, the gap is measured to the barrier of largest radial extent. The barrier or barriers may be perforated. At least one of the barriers may be a curved or angled plate. We have found that barrier means of or above this minimum axial extent provide efficient separation since little momentum exchange takes place across the barrier means. In absolute terms the separator will only separate out particles which are smaller than the width of the gap.
The barrier means is preferably mounted on a member which itself is mounted separately within the container and is closed off from fluid communication with said container. This member preferably extends throughout said region and may extend throughout said container. The member is preferably hollow and connected to receive relatively heavier phase components from a further separator connected to said outlet. The member preferably has a radius no more than 50% of the radius of the container when the latter is of circular section, and preferably less than 10%. One or both of the container and the body is/are preferably cylindrical. The outlet is preferably an annulus arranged around the member, whose radial width is between 5% and 50% of the radius of the member when cylindrical.
The lower portion of the container is preferably removable from the upper portion, so that it can be emptied of heavier phases in use. The container is preferably splitable between the portions about a plane below the barrier means. When the member is provided, the member is preferably splitable as well, and preferably about the same plane. The lower portions of the container and of the member are preferably integral.
Axially extending additional barrier(s) may be provided, sealed to said end of the container. The axial extent is preferably at least 10% of the diameter of the container at its closed end. The gap between the wall of the container and the or the outer barrier is preferably between 5% and 25% of the diameter of the container at its closed end.
The means for introducing the fluid mixture swirling about an axis is preferably arranged tangentially to the container and this tangential arrangement may be in the form of an involute. The involute may have an upstream radius which is between 30% and 300% larger than the downstream radius and preferably between 50% and 200%. The involute may comprise a series of segments (preferably at least three) of decreasing radius towards the container, the centres of the segments being arranged to produce a smooth transition from one segment to the next.
The outlet of lighter phases of the mixture preferably comprises a foraminated screen leading to an annular chamber surrounding said member. This screen is preferably frusto-conical, tapering outwardly in the downstream direction from the radius of said member to which it is sealed at its narrow end. The axial length of the screen is preferably between 50% and 150% of the outer diameter of the annular outlet duct. The screen preferably has a clear area of between 30% and 70% of its surface area.
The present invention has particular applicability in domestic vacuum cleaners, where dust and other debris are separated from air, although phase separation of other materials including separation of two liquids is envisaged.